Biomedical subjects

William E Garrett

Publications and source records attributed to William E Garrett.

23 records · Page 2Linked to original sources

PubMed2002

Electromyographic Analysis of Single-Leg, Closed Chain Exercises: Implications for Rehabilitation After Anterior Cruciate Ligament Reconstruction.

OBJECTIVE: Many knee rehabilitation studies have examined open and closed kinetic chain exercises. However, most studies focus on 2-legged, closed chain exercise. The purpose of our study was to characterize 1-legged, closed chain exercise in young, healthy subjects. SUBJECTS: Eighteen normal subjects (11 men, 7 women; age, 24.6 +/- 1.6 years) performed unsupported, 1-legged squats and step-ups to approximately tibial height. MEASUREMENTS: Knee angle data and surface electromyographic activity from the thigh muscles were recorded. RESULTS: The maximum angle of knee flexion was 111 +/- 23 degrees for squats and 101 +/- 16 degrees for step-ups. The peak quadriceps activation was 201 +/- 66% maximum voluntary isometric contraction, occurring at an angle of 96 +/- 16 degrees for squats. Peak quadriceps activation was 207 +/- 50% maximum voluntary isometric contraction and occurred at 83 +/- 12 degrees for step-ups. CONCLUSIONS: The high and sustained levels of quadriceps activation indicate that 1-legged squats and step-ups would be effective in muscle rehabilitation. As functional, closed chain activities, they may also be protective of anterior cruciate ligament grafts. Because these exercises involve no weights or training equipment, they may prove more cost effective than traditional modes of rehabilitation.

Journal Article↗

PubMedDate not supplied

Virtual reality simulation of arthroscopy of the knee.

The virtual reality arthroscopic knee simulator (VR-AKS) consists of a computer platform, a video display, and two force-feedback (haptic) interfaces known as "PHANToMs" that also monitor the position of the instruments in the user's hands. The forces that the user would normally apply to the lower limb during arthroscopy are directed through an instrumented surrogate leg. Proprietary software provides the mathematical representation of the physical world and replicates the visual, mechanical, and behavioral aspects of the knee. This includes moderating the haptic interface and simultaneously executing a collision-detection algorithm that prevents the instruments from moving through "solid" surfaces. Modeling software interacts with this algorithm to send the appropriate images to the video display, including knee pathology such as meniscal tears and chondral defects as well as normal anatomy. Task-oriented programs monitor specific performance such as executing a proper examination of the knee or shaving a torn meniscus.

Arthroscopy↗

PubMedDate not supplied

The repeatability of scapular rotations across three planes of humeral elevation.

Measurement of scapular kinematics is an important component in the assessment of shoulder function; however, repeatability of these measurements has not been established. The purpose of this study, therefore, was to determine the repeatability of scapular rotation measures for different humeral elevation planes between trials, sessions, and days. Three-dimensional scapular rotations were collected using an electromagnetic tracking system in three planes of humeral elevation. Coefficient of multiple correlation (CMC) values were calculated between trials, sessions, and days for curves of scapular rotations. CMC values were compared with repeated measures analysis of variance (ANOVAs) and Tukey's post-hoc procedures. Tests of simple main effects were performed for significant interaction effects. Our results suggest that scapular rotation measures are repeatable between trials within the same testing session, but less repeatable between testing sessions and days. Sagittal plane elevation consistently yielded the highest CMC values for all scapular rotations. These results suggest sagittal plane elevation should be considered to evaluate differences in scapular rotations.

Adult↗

PubMedDate not supplied

Intramedullary screw fixation of Jones fractures. Analysis of failure.

Treatment failures after screw fixation of Jones fractures are reported to be infrequent. Between 1993 and 1999, 15 patients (mean age, 21.7 years) underwent cannulated screw fixation of a Jones fracture at our institution. There were six treatment failures: four refractures and two symptomatic nonunions. The mean time to full activity was 6.8 weeks for the patients with failure compared with 9 weeks for patients who did not have complications. Although all patients were asymptomatic and radiographically progressing to union before return to full activity, only one of six patients with failures had complete radiographic union, compared with six of seven patients with no complications. There was a higher proportion of elite athletes (division I or professional level) among the failure group (83%) compared with those without complications (11%). There were no significant differences in age, sex, screw diameter, use of bone graft, or age of fracture between patients with failures and those without complications. Return to full activity, especially among elite athletes, before complete radiographic union was predictive of failure. Even though intramedullary screw fixation offers advantages over nonoperative treatment, a significant risk of postoperative complications exists.

Adolescent↗

PubMedDate not supplied

A comparison of knee kinetics between male and female recreational athletes in stop-jump tasks.

We compared the knee kinetics of 10 male and 10 female recreational athletes (aged 19 to 25 years) performing forward, vertical, and backward stop-jump tasks. Three-dimensional videography and force plate data were used to record the subjects' performance of the three stop-jump tasks, and an inverse dynamic procedure was used to estimate the knee joint resultant forces and moments. Women exhibited greater proximal anterior shear force than did men during the landing phase. All subjects exhibited greater proximal tibia anterior shear force during the landing phase of the backward stop-jump task than during the other two stop-jump tasks. Women also exhibited greater knee extension and valgus moments than did men during the landing phase of each stop-jump task. Men exhibited greater proximal tibia anterior shear force than did women during the takeoff phase of vertical and backward stop-jump tasks. These results indicate that female recreational athletes may have altered motor control strategies that result in knee positions in which anterior cruciate ligament injuries may occur. The landing phase was more stressful for the anterior cruciate ligament of both women and men than the takeoff phase in all stop-jump tasks. Technical training for female athletes may need to be focused on reducing the peak proximal tibia anterior shear force in stop-jump tasks. Further studies are needed to determine the factors associated with the increased peak proximal tibia anterior shear force in female recreational athletes.

Adult↗